bpo-35967: Baseline values for uname -p (GH-12824)

* Add a test intended to capture the expected values from 'uname -p'

* Instead of trying to keep track of all of the possible outputs on different systems (probably a fool's errand), simply assert that except for the known platform variance, uname().processor matches the output of 'uname -p'

* Use a skipIf directive

* Use contextlib.suppress to suppress the error. Inline strip call.